The massacre at Marjory Stoneman Douglas High School in South Florida left at least 17 people dead

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Samantha Grady was in her Holocaust class with her best friend Wednesday afternoon when they heard two shots fired outside the door of their classroom in Marjory Stoneman Douglas High School.

Soon, the gunman would approach, and that friend would become one of at least 17 people to die in the massacre at the high school in Parkland, Florida, one of the deadliest in U.S. history. Grady was wounded but escaped, she said in an emotional interview on the "Today" show Thursday morning, crediting something her friend told her with helping her survive the harrowing ordeal.

When they heard the first gunshots, the students in Grady's class ran for cover, the high school junior said.

"There was a big bookshelf and we all kind of huddled there together," Grady said. "We clamped really close tightly together."

The class stayed behind the bookshelf, pushing a cabinet in front of them as well to block some of the bullets. But soon the gunman came "came for our classroom," Grady said.

The door was locked, but he shot "quite a few bullets into the glass," according to Grady, hitting some people behind her.

The students ran, but before they did, Grady's best friend — who she didn't name — told her, "'Grab a book. Grab a book.' It was a tiny book, but I took it and held it up."

"My dad was really worried. It was etched all over his face. My mom, she was bawling. As you can imagine, it was pretty scary for both of them," Grady said.

Despite the death of her best friend, and her own wounds that must now heal, Samantha said she doesn't want that day to control her. She said the concern and support from her family is "nice" and has even formed a stronger bond between them.